Light-refracting material.



- State of'New York,

FRANK J; I TONE,

or NIAGARA rALLs, NEW YORK,

Assieuon TO THE cAaiaonuNnuu COMPANY, OF NIAGARA FALLS, NEW YORK, ACORPORATION OF PENNSYLVANIA No Drawing,

To all it concern: v

Be ,it' known that I, FRANK J. Tome, of Niagara- Falls, in the county ofNiagara,

and useful Light-Refracting Material, ofwhich the following is aspecification.

Silicon carbid or carborundum produce y furnace around a centralconductingcore of carb'onr'a mass of carbon in the form of ground cokemingled with sand, sawdust and common salt, passing the'currentthroughthe core and generating heat which causes the ,SlllCOIl and carbon tocombine and to produce a cylindrical zone of carborundum crystals.

The theoretical re'act1on according to which the process is carried onis-the following: SiO. 3C=SiC+2CO.

It has been the practice to use the ingredients of the charge mixture insubstantially the following proportions which afford a slight excess ofcarbon above that which is theoretically. required; ground coke, 35.1%;sand, 54c.45%;' sawdust, 7 common salt, 3.5%. The silicon'carbidproduced in this way occurs in the form of opaque crystals of variouscolors, the black predominating. Some of the crystals are blue andgreen, and some have iridescent surfaces showing colors of the spectrum.

1 I have discovered that silicon 'carbid can be produced in colorlesstransparent crystals which have great value in the arts because theirindex of refraction is very high, exceeding that of crown glass and thediamond, and in fact exceeding that of any known substance which istransparent tothe whole visible spectrum.[ Such crystals also possessdouble refraction and are-of great for they can be cut with regularfacets and polished. By selecting crystals of great depth. in thedirection of the optical axis they can be cut to form gems which utilizethe property of double refraction, and by utilization of the greatdispersion of the extraordinary production of interference colors,ford'great'brilliancy and beauty. I accomplish the manufacture of suchtransparent crystals of suflicient size to be utilized as gems and foroptical purposes by making Lmnr-nnrimorime MATERIAL.

v I Specification or iLe'tters Ratent.

- Application filed April 25-, 1908. Serial uaeaaisa to have anysubstantial the commercial methods heretofore ployed is made by charginginto an electric I 10 v n. reaction of great lmportance is a gaseouswhich start upon A ing this purpose the charge that the proper thosewhich exist in the crystalline zone of carbon core.

ray and. they af 'metallic oxids.

use,in a grea action'which as not been prev ously bearing upon formationthereact on by which 'siliconlcarbidi is or- &F i 2i moy5 i I s ihatthere/ inthe forma;

' an STATES P TENT Pate measure, of a "chemical ;re-'

known,

the 1 I fdinarily supposed to be formed, which is d expressed by theformula" tion' of crystals of large size which is ex'- pressed by thefollowing-formula: thereby an intense f p 3s +2oo=2sio+siQf I Thereaction expressed by this formula tue of the capacity ofisilicon toreduce car,- bon monoxid at certaintemperatures below that at whichsilicon carbid dissociates into silicon and carbon. In accordance withthis which carborundum dissociates. The necmonoxid, both existing asgases in the atm'os phere of the interior of the carborundum furnace,and their combination results in the production of crystalline siliconcarbid and silica in a volatile form. thus produced builds up 'in largecrystals, crystals initially formed by the direct union of the siliconand carbon of the charge mixture; and by prolongthe operation of thefurnace, these crystals' can be made to attain a large size Forconstituted so as to afford spaces for the mingling and combining of thegases, and the temperature should be less than that at which carborundumdisassoci-ates. The necessary space for circulation of the gases isafforded by using sawdust in the charge mixture, preferably in a largerpercentage than heretofore employed; and I have found temperatureconditions are a carborundum furnace just outside the Inthe preferablepractice of my inven 'tion I' make a carborundum furnace with a core ofcarbon preferably in the form of carbon granules, using for that purposecarbon which For this purpose I may use a carbon core taken from of afurnace, or I may prepare'the core specially bysubjecting it to electricheat, which mixture -should be" reaction and takes place by v1ri Thesilicon carbidf is free from contamination of previous runs 7 willvolatilize its containedoxids. I, surround this core witha mixture ofsilica, ground carbon and sawdust or like material, preferably addingcommon salt as aflux, and employ the silica and carbon in a'pure "state,free from metallic oxids, the carbon manufacture of carborundum, but Icontinue the operation for such time that the 'zone of carborundumcrystals adjacent tothe core'is vdecomposed to a considerable thickness,preferably to an extent of two or three lnches. The decomposition ofthese crystals results in the liberation of silicon vapor, whichcombines with the carbon monoxid gases in the furnace and builds uplarge crystals of carborundum just outside the zone of aphite which isformed by the decompositlon. The crystals thus produced are clear andtransparent, be ing free from coloration, and can be made of a largesize.

It is important that the carbon of the charge should not be in excess,since otherwise the crystals produced are apt to be black; but with carein the composition of the charge and the provision of for the gaseousreaction and by proper continuation of the time by those skilled in thespaces of the reaction, I am enabled to produce satisfactorily large,clear crystals of great commercial value.

By a ding to the charge mixture a small percentage of suitable coloringmaterial the crystals can be tinted without destroying theirtransparency. For this purpose I -may use oxid ofchromium or 01nd ofmanganese. These coloring oxids should be added only in small amount,say not more than one-half of one per cent. of the total charge.

The invention is capable of modification the art; and by the descrlptionof the preferred details of practice of the process I do not intend tolimit thereto the .broad claims of thisspeci-fication,

slnce What I claim is:

1. As a new article of manufacture, a crystal of silicon carbid,substantiallydeveloped in the direction of its optical axis. I

2. As a new article of manufacture, a

trans arent crystal of silicon carbid, substantially developed in thedirection of its optical axis.

3. As a new article of manufacture, a

transparent crystal of silicon carbid substantially developed in thedirection of its optical axis, having its surface cut and polished toform regular facets.

4. As a new article of manufacture, a transparent crystal of siliconcarbid sub stantially' developed in the direction of its optical axis,having its surface cut and" polished to form regular facets, said facetsbeing symmetrical with the optical axis of the crystal.

In testimony set my hand.

FRANK J. TONE.

Witnesses;

CLARENCE D. KERR, ANNA E. WALLACE.

whereof, I have hereunto

